Got it. (1) Yes, 500k is a lot, but (2) the TFRC program is making fairly expensive TPUs available at shockingly good prices for researchers willing to do so

Got it. (1) Yes, 500k is a lot, but (2) the TFRC program is making fairly expensive TPUs available at shockingly good prices for researchers willing to do some tire-kicking and feedback-providing. So 500k of TPU time is easier to come by than, say, 500k of generic compute.